my $nouser = 5;
my $suffix;

$suffix = 'st' if ($nouser =~ /(1)$/);
$suffix = 'nd' if ($nouser =~ /(2)$/);
$suffix = 'rd' if ($nouser =~ /(3)$/);
$suffix = 'th' if ($nouser =~ /(4|5|6|7|8|9|0)$/);
$suffix = 'th' if ($nouser =~ /(11|12|13)$/);

$nouser = $nouser . $suffix;